Basically, you just have to twist the chrome bezel so that the tangs on the back line up with the slots in the case. If you look at the back of the gauges, you see what I mean. I had a couple of bezels that were very tight, so I gently pried up the tangs a tad and that loosened the bezel up.
IIRC, there's one gauge that doesn't have the tangs and slots...ammeter I think. In that case, you'll have to pry the bezel all the way around to get it off. If you're careful you won't wreck the bezel.